To cope with this issue, prior works require full or partial knowledge of the CSI to perform the diagnosis.
The diagnostic technique proposed in [1]} requires full CSI, which assumes a free-space wireless channel and proposes to calculate the channel vector using known sub-path AOA and gain (i.e., \(\theta _l\)  and \(\alpha _l\) ).
Hence, one can generate the fault-free channel vector \(\mathbf {h}\)  using (REF ) and subtract it from the received signal, and the impact of channel can be eliminated.
A recent work [2]} relaxes the CSI requirement in the sense that it only requires the AOA of each sub-path (i.e., \(\theta _l\) ).
There the key idea is to project the received signal onto the null space of AOAs and thus the impact of channel can also be eliminated.
